The present invention relates to a new and improved construction of checking apparatus for documents for determining the identity or authenticity of the document and/or the identity of a person authorized to use the document.
Checking devices of such general type are employed to prevent the unauthorized use of, for instance, identification papers, contracts, currency, various types of obligations, bonds and other documents employed in transactions between individuals or when such documents are used in automatic installations. In a more restricted sense there are particularly checked with such type devices documents of a nature which exist only once i.e. single-copy documents and such devices enable checking their authenticity and/or the identity of the individual using the documents in order to determine his authority to do so.
In order to automatically check the authenticity of documents there have already been made numerous proposals both as concerns the actual formation of the document itself and also as concerns the checking devices needed to carry out the foregoing authentication and/or identity checking operations. These proposals enable checking a number of documents --for instance bank notes or currency-- but, however, do not allow for the positive identification of individual documents out of a group of similar documents.
Heretofore known documents containing individual, automatically readable data --for instance checks provided with a magnetic code or writing-- can be easily forged in a manner that it is possible to fool the automatic reader. Additionally, the forms used for the preparation of such documents which, for instance, may have come into the unlawful possession of an individual can be easily inscribed or marked by equipment which is relatively readily available in such a manner that the resultant documents can be neither automatically distinguished or even when visually inspected by other individuals from authentic or real documents.
Automatic equipment, such as for instance automatic banking devices for dispensing cash, are protected against the unlawful use of documents --typically for instance plastic cards-- which may have become lost or stolen in that they possess a keyboard or equivalent structure by means of which the user introduces into the system a secret character or number which is only known to the authorized owner or user of the card and compared with information which can be read-off of the document by means of a computer command or instructions. A prerequisite of such type system is that the computer command or instructions, which must be the same for all of the employed plastic cards and all of the automatic systems which are in operation, can be maintained secret, and particularly that the automatic systems can be constructed such that the devices provided within the automatic systems responsible for the computer commands are protected against improper access. A notable drawback of this method is that with modern techniques it is possible, even by using a relatively small number of documents with which there is associated the secret character or number, to determine the computer command or instructions which, for all heretofore known proposed systems always is constituted by a logical derivation, even if the same has a complicated origin.